The Post's great graphics team and photographers have put together a wonderful comparison of the inaugural crowds between 2009 and 2013.
Below, you can play with the photos by dragging the cursor back and forth, to get a sense for how the crowds compared.
(And make sure to check out all the graphics team's great before-and-after photos.)
The 2009 crowd was initially estimated at 1.8 million, though that number has since been revised downward to around 1 million, as the video below demonstrates.
Initial estimates of the 2013 crowd have suggested there were around 800,000 people.